Cheap strong dye with COOH group?
Dr Engelbert Buxbaum
(by engelbert_buxbaum from hotmail.com)
Mon Aug 8 18:56:42 EST 2011
In article <j1lokm$c74$1 from online.de>, novalidadress from nurfuerspam.de
> At Sun, 07 Aug 2011 04:04:41 +0000, DK wrote:
> > I actually didn't know that "regular" fluorescein has carboxy group.
> > What I meant was its carboxy derivative has another COO- on the same
> > ring. Fluorescein does bleach rather easily, so this might be a turn
> > off.
> Stupid me. The carboxy group I thought of is part of the chromophore. But
> that probably means that activating a second carboxy group for coupling
> (by eg a carbodiimide method) might result in a mess. That might be the
> reason, why fluorescin usually is used as isothiocyante (FITC) for
> Your suggestion with the food colorings might be worth a try.
> > Another thought: food coloring dyes. Of what Wikipedia lists, two
> > (erythrosine and tartrazine) are carboxylates. They should be very
> > cheap!
> > DK
FITC is used as the isothiocyanate group is very reactive towards
primary amines, allowing protein modification under mild conditions. The
resulting thiourea, however, has a somewhat limited stability.
Erythrosine btw is tetraiodo-fluoresceine.
If you plan experiments involving fluorescent labelling, your first stop
should be the the Molecular Probes Handbook
The-Handbook.html). For a more systematic introduction, you may also
consider "Biophysical Chemistry of Proteins" (Springer 2011) by yours
More information about the Methods